1. Field of the Invention
The present invention relates to an abnormality detecting device for detecting an abnormality in a current sensor and a voltage sensor, and more particularly to an abnormality detecting device for a current sensor for detecting current flowing to a secondary battery and for a voltage sensor for detecting battery voltage of the secondary battery.
2. Description of the Related Art
An electric vehicle or a hybrid electric vehicle obtaining vehicular driving force from an electric motor has a secondary battery installed and the electric motor is driven by electric power stored in the secondary battery. Such an electric vehicle is equipped with regenerative braking, namely, a braking function having the electric motor function as a generator during vehicular braking where the kinetic energy of the vehicle is converted into electrical energy. The converted electrical energy is stored into the secondary battery and is reused when performing acceleration.
Since battery performance deteriorates when the secondary battery is over-discharged or over-charged, it is necessary to adjust the charging and discharging operations by recognizing the state of charge (SOC) of the secondary battery. For devices for calculating the SOC of the secondary battery, a method is known for calculating the SOC on the basis of the terminal voltage of the secondary battery. However, since the terminal voltage varies according to current, devices equipped with a voltage sensor and a current sensor for calculating the SOC from both the terminal voltage and the current have been developed in recent years.
When an abnormality is generated at the current sensor in such a device mentioned hereinabove, the SOC of the secondary battery cannot be calculated. As a result, the discharging and the charging of the secondary battery cannot be appropriately controlled. Thus, a device for calculating the SOC having a current sensor is equipped with a device for detecting an abnormality of the current sensor.
Japanese Patent Laid-Open Publication No. 2000-206221 discloses a detecting device for judging a current sensor is abnormal when a voltage detected by a voltage sensor rises and falls at a predetermined frequency or more at a predetermined coefficient of fluctuation or more within a predetermined time while a current value detected by a current sensor continues to indicate approximately zero.
Furthermore, Japanese Patent Laid-Open Publication No. 2003-68366 discloses a detecting device for acquiring an estimated voltage change by multiplying a coefficient k, which is determined on the basis of SOC of a secondary battery, with a charging/discharging current detected by a current sensor, comparing the estimated voltage change with the change in terminal voltage obtained from an actual detected result of a voltage sensor, and issuing a report that there is a sensor abnormality when the difference exceeds a predetermined range.